Catalyst comprising a modified solid oxide

ABSTRACT

There is provided a catalyst comprising a hydrogenation/dehydrogenation component, such as a noble metal, and an acidic solid component comprising a Group IVB metal oxide modified with an oxyanion of a Group VIB metal. An example of this catalyst is zirconia, modified with tungstate and platinum. There is also provided a method for preparing this catalyst. This catalyst may be used, for example, to isomerize C 4  to C 8  paraffins. The feed to this paraffin isomerization reaction may, optionally, include cyclic hydrocarbons, such as benzene or cyclohexane, which may undergo ring opening reactions during the course of the isomerization reaction.

This application is a continuation of U.S. Ser. No. 08/095,884 filedJul. 22, 1993 and now abandoned.

There is provided a catalyst comprising a hydrogenation/dehydrogenationcomponent, such as a noble metal, and an acidic solid componentcomprising a Group IVB metal oxide modified with an oxyanion of a GroupVIB metal. This catalyst may be used, for example, to isomerize C₄ to C₈paraffins. The feed to this paraffin isomerization reaction may,optionally, include cyclic hydrocarbons, such as benzene or cyclohexane,which may undergo ring opening reactions during the course of theisomerization reaction.

The isomerization of paraffins, especially light paraffins, is anestablished refining process which is traditionally used to provideadditional feedstock for alkylation units or to convert relatively lowoctane linear paraffins to higher octane, branched chain isomers whichcan be blended into the gasoline pool. Straight chain paraffins such asn-butane, n-pentane and n-hexane are converted to the correspondingisoparaffins by various isomerization processes which may use varioustypes of catalysts.

Non-regenerable Lewis and Bronsted acid catalysts may be used, forexample, as disclosed in U.S. Pat. Nos. 3,766,286; 3,852,184; 3,855,346;3,839,489; 4,144,282; and 4,814,544. Commerical processes of this typehave been developed by various companies including Phillips PetroleumCompany (Catalytic Isomerization) and Shell Development Company (LiquidPhase Isomerization).

An alternative type of catalyst used in a number of commercialisomerization processes comprises a metal hydrogenation/dehydrogenationcomponent, usually platinum, on a porous support. An example of thisprocess is the Penex process (UOP) in which the isomerization is carriedout in the presence of hydrogen and a platinum catalyst. The Iso-Kelprocess (M. W. Kellogg) also employs a precious metal catalyst withhydrogen circulation and the Pentafining (Arco/Englehardt) and Butamer(UOP) processes also employ platinum on supports with external hydrogencirculation. Processes of this kind are disclosed, for example, in U.S.Pat. Nos. 4,834,866 (Schmidt) and U.S. Pat. No. 4,783,575 (Schmidt).

Isomerization processes utilizing metal components on supportscomprising a molecular sieve are disclosed in U.S. Pat. Nos. 3,842,114(Sie); U.S. Pat. No. 3,836,597 (Sie); U.S. Pat. No. 4,778,944 (Zarchy)and U.S. Pat. No. 4,374,296 (Haag).

Paraffin isomerization catalysts may also be employed as ring openingcatalysts for the removal of cyclic aromatic precursors from reformerfeedstocks as disclosed in U.S. Pat. No. 4,783,575 (Schmidt) and U.S.Pat. No. 4,834,866 (Schmidt). For example, cyclohexane, a precursor ofbenzene, may be isomerized to a mixture of branched paraffins which areonly partly aromatized in the reformer so as to minimize the productionof benzene. U.S. Pat. No. 3,631,117 describes a process for thehydroisomerization of cyclic hydrocarbons that uses a zeolite supportedGroup VIII metal as a catalyst for ring opening and paraffinisomerization. The utilization of paraffin isomerization for ringopening aromatic precursors, especially cyclohexane, is likely to becomemore important in the future as environmental regulations limit thearomatic content, particularly the benzene content, of motor gasoline.

SUMMARY

There is provided a catalyst comprising (i) ahydrogenation/dehydrogenation component comprising a noble metal and(ii) an acidic solid component comprising a Group IVB metal oxidemodified with an oxyanion of a Group VIB metal.

There is also provided a method for preparing this catalyst comprisingcomprising (i) a hydrogenation/dehydrogenation component comprising anoble metal and (ii) an acidic solid component comprising a Group IVBmetal oxide modified with an oxyanion of a Group VIB metal, said methodcomprising the steps of:

(a) contacting the hydroxide or hydrated oxide of a Group IVB metal withan aqueous solution comprising a source of an oxyanion of a Group VIBmetal under conditions sufficient to form a solid material comprisingoxygen, Group IVB metal and Group VI metal; and

(b) combining said solid material of step (a) with a source of a noblemetal.

There is also provided a process for converting an organic compound,e.g., a hydrocarbon, over a catalyst comprising (i) ahydrogenation/dehydrogenation component comprising a noble metal and(ii) an acidic solid component comprising a Group IVB metal oxidemodified with an oxyanion of a Group VIB metal.

EMBODIMENTS

The catalyst described herein comprises an oxide of a Group IVB metal,preferably zirconia or titania. This Group IVB metal oxide is modifiedin two ways. According to one modification, the Group IVB metal oxide ismodified with an oxyanion of a Group VIB metal, such as an oxyanion oftungsten, such as tungstate. The modification of the Group IVB metaloxide with the oxyanion of the Group VIB metal imparts acidfunctionality to the material. The modification of a Group IVB metaloxide, particularly, zirconia, with a Group VIB metal oxyanion,particularly tungstate, is described in U.S. Pat. No. 5,113,034; inJapanese Kokai Patent Application No. Hei 1 1989!-288339; and in anarticle by K. Arata and M. Hino in Proceedings 9th InternationalCongress on Catalysis, Volume 4, pages 1727-1735 (1988), the entiredisclosures of these publications are expressly incorporated herein byreference.

According to another modification of the Group IVB metal oxide describedherein, a hydrogenation/dehydrogenation component is combined with theGroup IV metal oxide. This hydrogenation/dehydrogenation componentimparts the ability of the material to catalyze the addition of hydrogento or the removal of hydrogen from organic compounds, such ashydrocarbons, optionally substituted with one or more heteroatoms, suchas oxygen, nitrogen, metals or sulfur, when the organic compounds arecontacted with the modified material under sufficient hydrogenation ordehydrogenation conditions.

Examples of hydrogenation/dehydrogenation components include the oxide,hydroxide or free metal (i.e., zero valent) forms of Group VIII metals(i.e., Pt, Pd, Ir, Rh, Os, Ru, Ni, Co and Fe), Group IVA metals (i.e.,Sn and Pb), Group VB metals (i.e., Sb and Bi) and Group VIIB metals(i.e., Mn, Tc and Re). The present catalyst comprises one or morecatalytic forms of one or more noble metals (i.e., Pt, Pd, Ir, Rh, Os orRu). Combinations of catalytic forms of such noble or non-noble metals,such as combinations of Pt with Sn, may be used. The valence state ofthe metal of the hydrogenation/dehydrogenation component is preferablyin a reduced valance state, e.g., when this component is in the form ofan oxide or hydroxide. The reduced valence state of this metal may beattained, in situ, during the course of a reaction, when a reducingagent, such as hydrogen, is included in the feed to the reaction.

For the purposes of the present disclosure, the expression, Group IVBmetal oxide modified with an oxyanion of a Group VIB metal, is intendedto connote a material comprising, by elemental analysis, a Group IVBmetal, a Group VIB metal and oxygen, with 30 more acidity than a simplemixture of separately formed Group IVB metal oxide mixed with aseparately formed Group VIB metal oxide or oxyanion. The present GroupIVB metal, e.g., zirconium, oxide modified with an oxyanion of a GroupVIB metal, e.g., tungsten, is believed to result from an actual chemicalinteraction between a source of a Group IVB metal oxide and a source ofa Group VIB metal oxide or oxyanion.

This chemical interaction is discussed in the aforementioned article byK. Arata and M. Hino in Proceedings 9th International Congress onCatalysis, Volume 4, pages 1727-1735 (1988). In this article, it issuggested that solid superacids are formed when sulfates are reactedwith hydroxides or oxides of certain metals, e.g., Zr. These superacidsare said to have the structure of a bidentate sulfate ion coordinated tothe metal, e.g., Zr. In this article, it is further suggested that asuperacid can also be formed when tungstates are reacted with hydroxidesor oxides of Zr. The resulting tungstate modified zirconia materials aretheorized to have an analogous structure to the aforementionedsuperacids comprising sulfate and zirconium, wherein tungsten atomsreplace sulfur atoms in the bidentate structure.

Although it is believed that the present catalysts may comprise thebidentate structure suggested in the aforementioned article by Arata andHino, the particular structure of the catalytically active site in thepresent Group IVB metal oxide modified with an oxyanion of a Group VIBmetal has not yet been confirmed, and it is not intended that thiscatalyst component should be limited to any particular structure.

Other elements, such as alkali (Group IA) or alkaline earth (Group IIA)compounds may optionally be added to the present catalyst to altercatalytic properties. The addition of such alkali or alkaline earthcompounds to the present catalyst may enhance the catalytic propertiesof components thereof, e.g., Pt or W, in terms of their ability tofunction as a hydrogenation/dehydrogenation component or an acidcomponent.

The Group IVB metal (i.e., Ti, Zr or Hf) and the Group VIB metal (i.e.,Cr, Mo or W) species of the present catalyst are not limited to anyparticular valence state for these species. These species may be presentin this catalyst in any possible positive oxidation value for thesespecies. Subjecting the catalyst, e.g., when the catalyst comprisestungsten, to reducing conditions, e.g., believed to be sufficient toreduce the valence state of the tungsten, may enhance the overallcatalytic ability of the catalyst to catalyze certain reactions, e.g.,the isomerization of n-hexane.

Suitable sources of the Group IVB metal oxide, used for preparing thepresent catalyst, include compounds capable of generating such oxides,such as oxychlorides, chlorides, nitrates, etc., particularly ofzirconium or titanium. Alkoxides of such metals may also be used asprecursors or sources of the Group IVB metal oxide. Examples of suchalkoxides include zirconium n-propoxide and titanium i-propoxide.Preferred sources of a Group IVB metal oxide are zirconium hydroxide,i.e., Zr(OH)₄, and hydrated zirconia. The expression, hydrated zirconia,is intended to connote materials comprising zirconium atoms covalentlylinked to other zirconium atoms via bridging oxygen atoms, i.e.,Zr-O-Zr, further comprising available surface hydroxy groups. Theseavailable surface hydroxyl groups are believed to react with the sourceof an anion of a Group IVB metal, such as tungsten, to form the presentacidic catalyst component. As suggested in the aformentioned article byK. Arata and M. Hino in Proceedings 9th International Congress onCatalysis, Volume 4, pages 1727-1735 (1988), precalcination of Zr(OH)₄at a temperature of from about 100° C. to about 400° C. results in aspecies which interacts more favorably with tungstate. Thisprecalcination is believed to result in the condensation of ZrOH groupsto form a polymeric zirconia species with surface hydroxyl groups. Thispolymeric species is referred to herein as a form of a hydratedzirconia.

Treatment of hydrated zirconia with a base solution prior to contactwith a source of tungstate may be preferable. More particularly, asdemonstrated in Examples recited hereinafter, especially in Examples16-25, refluxing hydrated zirconia in an NH₄ OH solution having a pH ofgreater than 7 was beneficial. Without wishing to be bound by anytheory, it is theorized that the base-treated, hydrated zirconia isbetter because it has higher surface area. It is also theoreticallypossible that the base treatment alters surface hydroxyl groups on thehydrated zirconia, possibly in a manner which promotes a more desirableinteraction with the source of tungstate later used.

Suitable sources for the oxyanion of the Group VIB metal, preferablymolybdenum or tungsten, include, but are not limited to, ammoniummetatungstate or metamolybdate, tungsten or molybdenum chloride,tungsten or molybdenum carbonyl, tungstic or molybdic acid and sodiumtungstate or molybdate.

The hydrogenation/dehydrogenation component of the present catalyst maybe derived from Group VIII metals, such as platinum, iridium, osmium,palladium, rhodium, ruthenium, nickel, cobalt, iron and mixtures of twoor more thereof. These components may optionally be mixed withcomponents derived from Group IVA metals, preferably Sn, and/orcomponents derived from Group VIIB metals, preferably rhenium andmanganese. These components may be added to the catalyst by methodsknown in the art, such as ion exchange, impregnation or physicaladmixture. For example, salt solutions of these metals may be contactedwith the remaining catalyst components under conditions sufficient tocombine the respective components. The metal containing salt ispreferably water soluble. Examples of such salts include chloroplatinicacid, tetraammineplatinum complexes, platinum chloride, tin sulfate andtin chloride.

The present catalyst may be prepared, for example, by impregnating thehydroxide or oxide, particularly the hydrated oxide, of the Group IVBmetal with an aqueous solution containing an anion of the Group VIBmetal, preferably tungstate or molybdate, followed by drying.Calcination of the resulting material may be carried out, preferably inan oxidizing atmosphere, at temperatures from about 500° C. to about900° C., preferably from about 700° C. to about 850° C., and morepreferably from about 750° C. to about 825° C. The calcination time maybe up to 48 hours, preferably for about 0.5-24 hours, and morepreferably for about 1.0-10 hours. In a most preferred embodiment,calcination is carried out at about 800° C. for about 1 to about 3hours. The hydrogenation/dehydrogenation component of the catalyst(e.g., Group VIII metal, Group VIIB metal, etc.) may be added after orbefore the calcination step by techniques known in the art, such asimpregnation, coimpregnation, coprecipitation, physical admixture, etc.The hydrogenation/dehydrogenation component may also be combined withthe remaining catalyst components before or after these remainingcomponents are combined with a binder or matrix material as describedhereinafter.

When a source of the hydroxide or hydrated oxide of zirconium is used,calcination, e.g., at temperatures greater than 500° C., of thecombination of this material with a source of an oxyanion of tungstenmay be needed to induce the theorized chemical reaction which impartsthe desired degree of acidity to the overall material. However, whenmore reactive sources of zirconia are used, it is possible that suchhigh calcination temperatures may not be needed.

In the present catalyst, of the Group IVB oxides, zirconium oxide ispreferred; of the Group VIB anions, tungstate is preferred; and of thehydrogenation/dehydrogenation components, platinum and/or platinum-tinare preferred.

Qualitatively speaking, elemental analysis of the present catalyst willreveal the presence of Group IVB metal, Group VIB metal and oxygen. Theamount of oxygen measured in such an analysis will depend on a number offactors, such as the valence state of the Group IVB and Group VIBmetals, the form of the hydrogenation/dehydrogenation component,moisture content, etc. Accordingly, in characterizing the composition ofthe present catalyst, it is best not to be restricted by any particularquantities of oxygen. In functional terms, the amount of Group VIBoxyanion in the present catalyst may be expressed as that amount whichincreases the acidity of the Group IVB oxide. This amount is referred toherein as an acidity increasing amount. Elemental analysis of thepresent catalyst may be used to determine the relative amounts of GroupIVB metal and Group VIB metal in the catalyst. From these amounts, moleratios in the form of XO₂ /YO₃ may be calculated, where X is said GroupIVB metal, assumed to be in the form XO₂, and Y is said Group VIB metal,assumed to be in the form of YO₃. It will be appreciated, however, thatthese forms of oxides, i.e., XO₂ and YO₃, may not actually exist, andare referred to herein simply for the purposes of calculating relativequantities of X and Y in the present catalyst. The present catalysts mayhave calculated mole ratios, expressed in the form of XO₂ /YO₃, where Xis at least one Group IVB metal (i.e., Ti, Zr, and Hf) and Y is at leastone Group VIB metal (i.e., Cr, Mo, or W), of up to 1000, e.g., up to300, e.g., from 2 to 100, e.g., from 4 to 30.

The amount of hydrogenation/dehydrogenation component may be that amountwhich imparts or increases the catalytic ability of the overall materialto catalytically hydrogenate or dehydrogenate a hydrogenatable ordehydrogenatable organic compound under sufficient hydrogenation ordehydrogenation conditions. This amount is referred to herein as acatalytic amount. Quantitatively speaking, the present catalyst maycomprise, for example, from about 0.001 to about 5 wt %, e.g., fromabout 0.1 to about 2 wt %, of the hydrogenation/dehydrogenationcomponent, especially when this component is a noble metal.

The catalyst described herein may be used as a catalyst for isomerizingC₄ to C₈ paraffins. Suitable feeds contain substantial amounts of normaland/or singly branched low octane C₄ to C₈ hydrocarbons. The feed mayalso contain appreciable amounts of C₆ and C₇ cyclic paraffins which mayundergo ring-opening reactions.

The present isomerization process may be carried out by contacting thehydrocarbon feed in either liquid or gas phase with the solid catalystat temperatures less than 500° C., preferably less than 350° C.,preferably less than 300° C., and at pressure in the range from 1 to 200atmospheres, preferably from 1 to 100 atmospheres, more preferably 5 to50 atmospheres. The isomerization process may be carried out either inthe presence or absence of hydrogen, more preferably in the presence ofhydrogen. The mole ratio of hydrogen to hydrocarbon is preferably in therange of 0.01:1 to 10:1.

It may be desirable to incorporate the present catalyst with anothermaterial to improve its properties. Such materials include active andinactive materials and synthetic or naturally occurring zeolites as wellas inorganic materials such as clays, silica, and/or metal oxides. Thelatter may be either naturally occurring or in the form of gelatinousprecipitates, sols, or gels including mixtures of silica and metaloxides.

It is noted that the present catalyst need not contain any sulfate ion(U.S. Pat. No. 4,918,041), and is believed to be more stable and also tobe much easier to regenerate than sulfated catalysts, such as thesuperacid sulfated catalysts referred to in the aforementioned articleby K. Arata and M. Hino in Proceedings 9th International Congress onCatalysis, Volume 4, pages 1727-1735 (1988).

In the present isomerization process, n-paraffinic and mono-methylbranched paraffinic components are isomerized to higher branchedparaffins which are generally better octane boosters. By way ofillustration, the significance of these reactions can be gleaned from areview of the following table of Octane Numbers of Pure Hydrocarbonsfrom P. H. Emmett, ed., Catalysis, Vol. VI (1958).

    ______________________________________                                        Octane Numbers of Pure Hydrocarbons                                                          Blending Research Octane                                       Hydrocarbon    Number (clear)                                                 ______________________________________                                        Paraffins:                                                                    n-heptane       0                                                             2-methylhexane 41                                                             3-methylhexane 56                                                             2,2-dimethylpentane                                                                          89                                                             2,3-dimethylpentane                                                                          87                                                             2,2,3-trimethylbutane                                                                        113                                                            ______________________________________                                    

The feedstock for the present process may be one which containssignificant amounts of C₅ + normal and/or slightly branched paraffins.In addition, the feedstock may contain monocyclic aromatic compoundsand/or cyclic paraffins, such as cyclohexane. Among the hydrocarbonshaving 6 or less carbon atoms in the feedstock, at least 1 wt. %, e.g.,at least 5 wt. %, e.g., at least 10 wt. %, e.g., at least 20 wt. %,e.g., at least 30 wt. %, of these hydrocarbons may be cyclichydrocarbons, e.g., aromatics or cyclic paraffins.

The present catalyst may be used to isomerize C₄ -C₈ paraffinhydrocarbons, either as pure compounds or mixtures. In refineryoperations, the paraffins will normally be present in mixtures and, inaddition to the C₄ -C₈ materials, may contain hydrocarbons boilingoutside this range; cycloparaffins and aromatics may also be present.Thus, the feed will comprise C₄ -C₈ paraffins such as butane, pentane,hexane and these may be present in refinery streams such as raffinatecuts from solvent extraction units, reformer feedstock or pyrolysisgasoline from ethylene crackers. The feeds may also contain cyclichydrocarbons, e.g., in the form of C₆ + naphthas; the cyclic materialsin such feeds may undergo ring opening reactions in the presence of thecatalyst with its associated metal component, to form paraffins whichthen undergo isomerization to iso-paraffins which can be separated fromthe cyclics by fractionation with the cyclics being recycled toextinction. In addition to pure paraffin feeds (C₄ -C₈), mixedparaffin-olefin feeds containing significant levels of olefin may beutilized. The isomerization is carried out in the presence of thecatalyst, preferably in the presence of hydrogen. Reaction temperaturesare suitably in the range of about 200° to 800° F. (about 93° to 425°C.); temperatures outside this range may be utilized although they arenormally less preferred; temperatures from about 300° to 700° F. (about149° to 370° C.) are typical. Pressures will normally be up to about1000 psig (about 7,000 kPa abs.) although there is no reason why higherpressures should not be utilized. Lower pressures, in the range of about50 to 100 psig (about 445 to 790 kPa abs.) may readily be employed andthe use of relatively low pressures within this range will generally bepreferred in order to permit the use of low pressure equipment. Theisomerization is usually carried out in the presence of hydrogen,typically at a molar ratio relative to the feed from 0.01 to 10:1 andusually from 0.5:1 to 2:1. Space velocities are typically from 0.1 to 10LHSV and usually from 0.5 to 5 LHSV. When an additional acidic material(Lewis acid or Br.o slashed.nsted acid) is included in the catalyst,lower operational temperatures may be used, favoring the isomerizationover the less desired cracking reactions.

The noble metal component of the present catalyst provides ahydrogenation-dehydrogenation component to the catalyst. Metals having astrong hydrogenation function are preferred, especially platinum and theother noble metals such as palladium, rhodium, iridium, rhenium,although other metals capable of acting as a hydrogenation component mayalso be used, for example, nickel, tungsten or other metals of GroupVIIIA of the Periodic Table (IUPAC Table), either singly, in mixtures orin combination with other metals. The amount of the noble metalcomponent may be in the range 0.001 to 5 wt. % of the total catalyst,e.g., from 0.1 to 2 wt. %. Base metal hydrogenation components may beadded in somewhat greater amounts. The hydrogenation component can beexchanged onto the support material, impregnated into it or physicallyadmixed with it. If the metal is to be impregnated into or exchangedonto the support, it may be done, for example, by treating the supportwith a platinum metal-containing ion. Suitable platinum compoundsinclude chloroplatinic acid, platinous chloride and various compoundscontaining the platinum ammine complex. The metal compounds may beeither compounds in which the metal is present in the cation or anion ofthe compound; both types of compounds can be used. Platinum compounds inwhich the metal is in the form of a cation of cationic complex, e.g.,Pt(NH₃)₄ Cl₂ are particularly useful, as are anionic complexes such asthe vanadate and metatungstate ions. Cationic forms of other metals arealso useful since they may be exchanged onto the support or impregnatedinto it.

The catalyst may be subjected to a final calcination under conventionalconditions in order to dehydrate the catalyst and to confer the requiredmechanical strength on the catalyst. Prior to use the catalyst may besubjected to presulfiding.

When a source of hydrogenation metal, such as H₂ PtCl₆, is used as asource of a hydrogenation/dehydrogenation component in the presentcatalyst, it may be desirable to subject the present catalyst toextended reducing conditions, e.g., lasting more than 4 hours. Benefitsof such extended reducing conditions are demonstrated in Examples whichfollow, especially in Examples 26-38.

Higher isomerization activity may be provided by the inclusion of anadditional material having Lewis or Br.o slashed.nsted acid activity inthe catalyst, especially when the catalyst comprises a porous bindermaterial. For this purpose, both liquid and solid acid materials may beused. Examples of suitable additional acidic materials include aluminumtrichloride, boron trifluoride and complexes of boron trifluoride, forexample, with water, lower alcohols or esters. The maximum amount whichmay be added is set by the ability of the support material, especiallythe binder material, to sorb the added component and is readilydetermined by experiment.

The present catalyst may be used as the exclusive isomerization catalystin single or multiple catalyst beds or it may be used in combinationwith other isomerization catalysts. For example, a feed may be firstcontacted with a catalyst bed comprising the present catalyst followedby contact with a second catalyst bed comprising a different catalyst,such as Pt on mordenite, Pt on zeolite beta or a chloridedplatinum-alumina catalyst, as described in U.S. Pat. Nos. 4,783,575 and4,834,866. The temperature of the first catalyst bed may be higher thanthe temperature of the second catalyst bed. When the present catalyst iscalled upon to cause extensive ring opening, especially in an initialcatalyst bed, relatively high temperatures, e.g., as high as 500° C.,and/or relatively high pressures, e.g., as high as 200 atmospheres, maybe employed.

The present catalyst can be shaped into a wide variety of particlesizes. Generally speaking, the particles can be in the form of a powder,a granule, or a molded product, such as an extrudate having particlesize sufficient to pass through a 2 mesh (Tyler) screen and be retainedon a 400 mesh (Tyler) screen. In cases where the catalyst is molded,such as by extrusion, the catalyst can be extruded before drying orpartially dried and then extruded. The present catalyst may becomposited with a matrix material to form the finished form of thecatalyst and for this purpose conventional matrix materials such asalumina, silica-alumina and silica are suitable with preference given tosilica as a non-acidic binder. Other binder materials may be used, forexample, titania, zirconia and other metal oxides or clays. The activecatalyst may be composited with the matrix in amounts from 80:20 to20:80 by weight, e.g., from 80:20 to 50:50 active catalyst:matrix.Compositing may be done by conventional means including mulling thematerials together followed by extrusion of pelletizing into the desiredfinished catalyst particles.

The catalyst may be treated by conventional pre-sulfiding treatments,e.g., by heating in the presence of hydrogen sulfide, to convert oxideforms of the metal components to their corresponding sulfides.

Although the use of the present catalyst in isomerization reactions hasbeen emphasized hereinabove, it will be appreciated that this catalystis useful for a variety of organic, e.g., hydrocarbon, compoundconversion processes, especially those requiring the use of adual-functional (1) acidic and (2) hydrogenation/dehydrogenationcatalyst. Such conversion processes include, as non-limiting examples,hydrocracking hydrocarbons with reaction conditions including atemperature of from about 100° C. to about 700° C., a pressure of fromabout 0.1 atmosphere (bar) to about 30 atmospheres, a weight hourlyspace velocity of from about 0.1 to about 20, and a hydrogen/hydrocarbonmole ratio of from about 0 to about 20; dehydrogenating hydrocarboncompounds with reaction conditions including a temperature of from about300° C. to about 700° C., a pressure of from about 0.1 atmosphere toabout 10 atmospheres and a weight hourly space velocity of from about0.1 to about 20; converting paraffins to aromatics with reactionconditions including a temperature of from about 100° C. to about 700°C., a pressure of from about 0.1 atmosphere to about 60 atmospheres, aweight hourly space velocity of from about 0.5 to about 400 and ahydrogen/hydrocarbon mole ratio of from about 0 to about 20; convertingolefins to aromatics, e.g., benzene, toluene and xylenes, with reactionconditions including a temperature of from about 100° C. to about 700°C., a pressure of from about 0.1 atmosphere to about 60 atmospheres, aweight hourly space velocity of from about 0.5 to about 400 and ahydrogen/hydrocarbon mole ratio of from about 0 to about 20;transalkylating aromatic hydrocarbons in the presence ofpolyalkylaromatic hydrocarbons with reaction conditions including atemperature of from about 200° C. to about 500° C., a pressure of fromabout atmospheric to about 200 atmospheres, a weight hourly spacevelocity of from about 10 to about 1000 and an aromatichydrocarbon/polyalkylaromatic hydrocarbon mole ratio of from about 0.3/1to about 20/1, and a hydrogen/hydrocarbon mole ratio of from about 0 toabout 20; and transferring hydrogen from paraffins to olefins withreaction conditions including a temperature from about -25° C. to about400° C., e.g., from about 75° C. to about 200° C., a pressure from belowatmospheric to about 5000 psig, e.g., from about atmospheric to about1000 psig, a mole ratio of total paraffin to total olefin of from about1:2 to about 500:1, e.g., from about 5:1 to about 100:1; and a weighthourly space velocity based on olefin of from about 0.01 to about 100,e.g., from about 0.05 to about 5.

The present catalyst may also be used in various hydroprocessingreactions, such as the removal of metals, nitrogen and/or sulfur fromfeedstocks, such as resids, including such elements, particularly in theform of heteroatoms. These hydroprocessing reactions comprise contactingthe feedstock along with a sufficient amount of hydrogen with thepresent catalyst under conditions sufficient to remove metals, nitrogen,and/or sulfur.

EXAMPLE 1

This Example describes the preparation of a tungstate modified zirconiacatalyst. One part by weight of zirconyl chloride, ZrOCl₂.8H₂ O, wasadded to 3 parts by weight of a 10M NH₄ OH solution. The resultingslurry, Zr(OH)4, was filtered and washed with 5 parts of distilleddeionized water, then air dried at 140° C. for 8 hours. Approximately7.5 parts by weight of the resulting Zr(OH)₄ were impregnated viaincipient wetness with 2.2 parts of an aqueous solution containing 1part of ammonium metatungstate, (NH₄)₆ H₆ W₁₂ O₄₀. The resultingmaterial was dried for 2 hours at 120° C. and then calcined at 800° C.in flowing air for 2 hours. The sample was calcined at 500° C. for 1hour under flowing nitrogen prior to catalytic testing. This sample hada calculated mole ratio of ZrO₂ /WO₃ of 11.6.

EXAMPLE 2

A platinum and tungstate modified zirconia catalyst was prepared byincipient wetness co-impregnation of H₂ PtCl₆ and (NH₄)₆ H₆ W₁₂ O₄₀ ontoZr(OH)₄. More particularly, to 181.8 parts by weight of Zr(OH)₄ wereadded, via incipient wetness impregnation, 54.5 parts of an aqueoussolution containing 24.4 parts of (NH₄)₆ H₆ W₁₂ O₄₀ and 1 part of H₂PtCl₆. The resulting material was then dried for 2 hours at 120° C., andthen air calcined at 800° C. for 2 hours. This platinum-containingcatalyst was calcined at 500° C. for 1 hour in flowing nitrogen and thenreduced with flowing hydrogen at 300° C. for approximately 2 hours priorto catalytic testing. This catalyst had a calculated mole ratio of ZrO₂/WO₃ of 11.6 and contained 100 ppm of Pt based on the total weight ofthe catalyst.

EXAMPLE 3

A catalyst was prepared in the same manner as in Example 2 except thatmore H₂ PtCl₆ was used in the co-impregnation step. This catalyst had acalculated mole ratio of ZrO₂ /WO₃ of 11.6 and contained 0.2 wt. % of Ptbased on the total weight of the catalyst.

EXAMPLE 4

A catalyst was prepared in the same manner as in Example 2 except thatmore H₂ PtCl₆ was used in the co-impregnation step. This catalyst had acalculated mole ratio of ZrO₂ /WO₃ of 11.6 and contained 2 wt. % of Ptbased on the total weight of the catalyst.

EXAMPLES 5-8

The catalysts of Examples 1-4 were tested in the isomerization ofn-hexane. The n-hexane isomerization reactions were carried out in afixed-bed down-flow reactor. Liquid n-hexane was fed into the reactorusing a high pressure pump. Hydrogen was charged through a mass flowcontroller. Products were analyzed by gas chromatography. Theexperiments were performed at 260° C., LHSV=1.8 cc n-C₆ per cc catalystper hour, 450 psig, and a H₂ /n-C₆ mol ratio of 1.4.

The experimental results shown in Table 1 indicate that the addition ofsmall amounts of platinum to the catalyst greatly improves the n-hexaneisomerization activity to yield the desirable high-octane dimethylbutanes.

In the Tables which follow, the following abbreviations will beunderstood: n-C₆ (n-hexane); 3-MP (3-methylpentane); 2-MP(2-methylpentane); 2,3-DMB (2,3-dimethylbutane); 2,2-DMB(2,2-dimethylbutane); i-C₅ (isopentane); n-C₅ (n-pentane); C₄-(hydrocarbons having 4 or less carbon atoms); C₇ + (hydrocarbons having7 or more carbon atoms); CH (cyclohexane); MCP (methylcyclopentane); BZ(benzene); C₃ - (hydrocarbons having 3 or less carbon atoms); i-C₄(isobutane); n-C₄ (n-butane); and C₅ + (hydrocarbons having 5 or morecarbon atoms).

                                      TABLE 1                                     __________________________________________________________________________              Conv.                                                               Example                                                                            Catalyst                                                                           (wt. %)                                                                           n-C.sub.6                                                                        3-MP                                                                             2-MP                                                                             2,3-DMB                                                                            2,2-DMB                                                                            i-C.sub.5                                                                        n-C.sub.5                                                                        C.sub.4 --                                                                       Other*                              __________________________________________________________________________    5    Example 1                                                                          67.1                                                                              32.9                                                                             19.1                                                                             28.9                                                                             7.8  3.7  2.9                                                                              0.6                                                                              2.0                                                                              2.0                                 6    Example 2                                                                          73.2                                                                              26.8                                                                             21.3                                                                             32.2                                                                             8.8  4.7  2.5                                                                              0.5                                                                              1.2                                                                              2.0                                 7    Example 3                                                                          79.9                                                                              20.1                                                                             20.3                                                                             30.0                                                                             8.0  9.3  4.9                                                                              1.6                                                                              3.4                                                                              2.2                                 8    Example 4                                                                          84.3                                                                              15.7                                                                             18.7                                                                             29.1                                                                             8.5  15.5 5.4                                                                              1.7                                                                              2.3                                                                              3.2                                 __________________________________________________________________________     *Other is C.sub.7 +, cyclohexane (CH), and methylcyclopentane (MCP)      

EXAMPLES 9 and 10

The catalyst of Example 3 (0.2 wt. % Pt and a calculated mole ratio ofZrO₂ /WO₃ of 11.6) was tested at lower temperature, 220° C., and lowerLHSV. The results are presented in Table 2 and indicate that high yieldsof isomerate are obtained.

                                      TABLE 2                                     __________________________________________________________________________         LHSV                                                                              Conv.                                                                Example                                                                            (hr.sup.-1)                                                                       (wt. %)                                                                           n-C.sub.6                                                                        3-MP                                                                             2-MP                                                                             2,3-DMB                                                                            2,2-DMB                                                                            i-C.sub.5                                                                        n-C.sub.5                                                                        C.sub.4 -                                                                        Other*                               __________________________________________________________________________    9    0.4 86.4                                                                              13.6                                                                             16.8                                                                             26.5                                                                             7.8  16.7 8.0                                                                              2.8                                                                              4.8                                                                              2.9                                  10   0.6 83.1                                                                              16.9                                                                             20.1                                                                             31.8                                                                             9.3  11.7 3.7                                                                              0.7                                                                              2.5                                                                              3.2                                  __________________________________________________________________________     *Other is C.sub.7 +, cyclohexane (CH), and methylcyclopentane (MCP)      

EXAMPLE 11

In this Example platinum was added to the tungstate modified zirconiamaterial after the 800° C. air calcination step. 72.5 parts by weight ofZr(OH)₄, preparation given in Example 1, were impregnated with 21.7parts of an aqueous solution containing 12.2 parts of (NH₄)₆ H₆ W₁₂ O₄₀.The resulting material was dried for 2 hours at 120° C. and thencalcined in air at 800° C. for 2 hours. After cooling to roomtemperature, a second incipient wetness impregnation was performed; thistime, 1 part of H₂ PtCl₆ dissolved in 21.7 parts of distilled water wereadded. The catalyst was dried at 120° C. for 2 hours, calcined inflowing air at 350° C. for 3 hours, and then reduced with hydrogen at300° C. for approximately 2 hours. This catalyst contained 0.5 wt. % ofPt based on the total weight of the catalyst.

EXAMPLE 12

The platinum and tungstate modified catalyst of Example 11 was testedfor n-hexane isomerization at 260° C., 450 psig, LHSV=0.6 hr⁻¹, and a H₂/n-C₆ mole ratio of 1.4. Results are given in Table 3.

                                      TABLE 3                                     __________________________________________________________________________              Conv.                                                               Example                                                                            Catalyst                                                                           (wt. %)                                                                           n-C.sub.6                                                                        3-MP                                                                             2-MP                                                                             2,3-DMB                                                                            2,2-DMB                                                                            i-C.sub.5                                                                        n-C.sub.5                                                                        C.sub.4 --                                                                       Other*                              __________________________________________________________________________    12   Example                                                                            83.4                                                                              16.6                                                                             19.6                                                                             29.9                                                                             8.3  17.5 3.4                                                                              1.5                                                                              2.9                                                                              traces                                   11                                                                       __________________________________________________________________________     *Other is C.sub.7 +, cyclohexane (CH), and methylcyclopentane (MCP)      

EXAMPLE 13

Zirconium hydroxide, Zr(OH)₄, was synthesized by rapidly hydrolyzingZr(O)Cl₂ in a 10M NH₄ OH solution. The slurry was then pulverized for 30minutes, filtered, washed with DI water, vacuum dried for 4 hours, anddried at 140° C. for 8 hours.

Tungstate modified zirconia was prepared by impregnating Zr(OH)₄ withammonium metatungstate, (NH₄)₆ H₆ W₁₂ O₄₀. Drying of the resultantsample was performed for 2 hours at 120° C. and then calcined at 800° C.The material was cooled down to ambient temperature before Pt was addedvia incipient wetness using H₂ PtCl₆. The platinum-containing catalystwas calcined at 400° C. for 2 hours in flowing air, and then reducedwith flowing hydrogen at 300° C. for approximately 2 hours. The catalysthad a calculated mole ratio of ZrO₂ /WO₃ of 11.6 and contained 0.5 wt. %Pt based on the total weight of the catalyst.

EXAMPLES 14 and 15

These Examples illustrate the results obtained on simultaneous ringopening of C₆ cyclic hydrocarbons and n-hexane isomerization over thecatalyst of Example 13. A synthetic feedstock having the compositiongiven in Table 4 was used in these experiments. The product compositionand operating conditions are presented in Table 5. Results indicate thatthe catalyst of this invention exhibits high activity for ring opening,while maintaining high C₅ + yield and high paraffin isomerizationselectivity to more highly branched paraffins.

                  TABLE 4                                                         ______________________________________                                        FEED COMPOSITION                                                              Component          Wt. %                                                      ______________________________________                                        n-Hexane (n-C.sub.6)                                                                             50.0                                                       Methylcyclopentane (MCP)                                                                         14.5                                                       Cyclohexane (CH)   31.7                                                       Benzene (BZ)       3.9                                                        ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Example             2       3                                                 ______________________________________                                        Reaction Conditions                                                           Reactor temperature (°C.)                                                                  260     288                                               Reactor pressure (psig)                                                                           450     450                                               LHSV (hr.sup.-1)    0.54    0.54                                              H.sub.2 /C.sub.6 -mixture (mol/mol)                                                               2       2                                                 Product Composition (wt. %)                                                   C.sub.3 -           tr      0.7                                               i-C.sub.4           1.3     5.3                                               n-C.sub.4           0.4     2.0                                               i-C.sub.5           2.4     7.5                                               n-C.sub.5           0.9     3.7                                               2,2-DMB             9.3     11.4                                              2,3-DMB             6.1     6.2                                               2-MP                22.3    22.8                                              3-MP                14.7    15.3                                              n-C.sub.6           12.6    13.5                                              MCP                 20.4    8.4                                               CH                  6.3     2.0                                               BZ                  0       0                                                 C.sub.7 +           3.3     1.1                                               C.sub.5 + Yield (wt. %)                                                                           98.3    92.0                                              Reactant Conversion (%)                                                       Ring Opening        46.6    79.2                                              n-C.sub.6           74.8    73.0                                              ______________________________________                                    

EXAMPLE 16

This Example describes the preparation of a hydrous ZrO₂ support. Onepart by weight of zirconyl chloride, ZrOCl₂, 8H₂ O, was dissolved in 10parts H₂ O and concentrated NH₄ OH.sub.(aq) added until the solution pHwas ˜9. The resulting slurry, Zr(OH)₄, was filtered and washed with 10parts of distilled, deionized water. The solid was air dried at 130° C.for 16 hours.

EXAMPLE 17

This Example describes the preparation of a WO_(x) ZrO₂ catalyst fromthe zirconia support described in Example 16. Approximately 5.6 parts byweight of the dried product from Example 16 was impregnated viaincipient wetness with 4.2 parts of an aqueous solution containing 1part of ammonium metatungstate, (NH₄)₆ H₆ W₁₂ O₄₀. The resultingmaterial was dried in air and then calcined at 825° C. in air for 3hours.

EXAMPLE 18

This Example describes the preparation and use of a Pt/WO_(x) /ZrO₂catalyst from the resultant product described in Example 17. To 1 partof an 8% H₂ PtCl₆ solution was added 2.5 parts of H₂ O. This mixture wasthen used to impregnate by incipient wetness 7 parts of the driedproduct (at 130° C.) from Example 17. The catalyst was then calcined at300° C. in air for 2 hours. This catalyst was designated Catalyst A. Inthe catalytic experiments, Catalyst A was reduced with H₂ (100 cc/min)at 300° C. and atmospheric pressure for 4 hours. The unit was thenbrought to the desired conditions and hexane feed introduced. Catalyticdata and results are given in Table 6.

EXAMPLE 19

This Example describes the preparation of another WO_(x) /ZrO₂ catalystusing the zirconia support described in Example 16. Approximately 2.4parts by weight of the dried product from Example 16 was impregnated viaincipient wetness with 2.6 parts of an aqueous solution containing 1part of ammonium metatungstate. The resulting material was dried in airand then calcined at 825° C. in air for 3 hours.

EXAMPLE 20

This Example describes the preparation and use of a Pt/WO_(x) /ZrO₂catalyst from the resultant product described in Example 19. To 1 partof an 8% H₂ PtCl₆ solution was added 2.5 parts of H₂ O. This mixture wasthen used to impregnate by incipient wetness 7 parts of the driedproduct (at 130° C.) from Example 19. The catalyst was then calcined at300° C. in air for 2 hours. This catalyst was designated Catalyst B. Inthe catalytic experiments, Catalyst B was reduced with H₂ (100 cc/min)at 300° and atmospheric pressure for 18 hours. The unit was then broughtto the desired conditions and hexane feed introduced. Catalytic data andresults are given in Table 7.

EXAMPLE 21

This Example describes the preparation of the base-treated zirconiasupport. One part by weight of the filtered wet cake from Example 16 wasmixed with 10 parts of distilled, deionized water and the pH of themixture set to pH ˜9 with concentrated NH₄ OH.sub.(aq). This mixture wasrefluxed for 16 hours, cooled, filtered, and washed with 10 parts ofwater. The solid was air dried at 130° C. for 16 hours.

EXAMPLE 22

This Example describes the preparation of a WO_(x) /ZrO₂ catalyst fromthe zirconia support described in Example 21. Approximately 5.6 parts byweight of the dried product from Example 21 was impregnated viaincipient wetness with 4.2 parts of an aqueous solution containing 1part of ammonium metatungstate. The resulting material was dried in airand then calcined at 825° C. in air for 3 hours.

EXAMPLE 23

This Example describes the preparation and use of a Pt/WO_(x) /ZrO₂catalyst from the resultant product in Example 22. To 1 part of an 8% H₂PtCl₆ solution was added 2.5 parts of H₂ O. This mixture was then usedto impregnate by incipient wetness 7 parts of the dried product (at 130°C.) from Example 22. The catalyst was then calcined at 300° C. in airfor 2 hours. This catalyst was designated Catalyst C. In the catalyticexperiments, Catalyst C was reduced with H₂ (100 cc/min) at 300° C. andatmospheric pressure for 4 hours. The unit was then brought to thedesired conditions and hexane feed introduced. Catalytic data andresults are given in Table 8.

EXAMPLE 24

This Example describes the preparation of another WO_(x) /ZrO₂ catalystusing the zirconia support described in Example 21. Approximately 3.4parts by weight of the dried product from Example 21 was impregnated viaincipient wetness with 2.6 parts of an aqueous solution containing 1part of ammonium metatungstate. The resulting material was dried in airand then calcined at 825° C. in air for 3 hours.

EXAMPLE 25

This Example describes the preparation and use of a Pt/WO_(x) /ZrO₂catalyst from the resultant product described in Example 24. To 1 partof an 8% H₂ PtCl₆ solution was added 2.5 parts of H₂ O. This mixture wasthen used to impregnate by incipient wetness 7 parts of the driedproduct (at 130° C.) from Example 24. The catalyst was then calcined at300° C. in air for 2 hours. This catalyst was designated Catalyst D. Inthe catalytic experiments, Catalyst D was reduced with H₂ (100 cc/min)at 300° C. and atmospheric pressure for 18 hours. The unit was thenbrought to the desired conditions and hexane feed introduced. Catalyticdata and results are given in Table 9.

At comparable H₂ reduction times, the catalysts which were treated byheating with base solution (Catalysts C and D) showed improved yields ofthe isomerized 2,2-dimethylbutane product over the untreated catalysts(Catalysts A and B) at varying temperatures.

                  TABLE 6                                                         ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst A                       Temperature, °C.                                                                          230    240                                                 Pressure, psig     450    450                                                 LHSV               0.6    0.6                                                 H.sub.2 /HC        1.4/1  1.4/1                                               Hexane conv., wt. %                                                                              70.6   77.9                                                Selectivity, wt. %                                                            C.sub.1 -C.sub.5   0.5    0.8                                                 2,2-dimethylbutane 7.9    11.6                                                2,3-dimethylbutane 11.1   12.0                                                2-methylpentane    49.3   46.1                                                3-methylpentane    31.2   29.5                                                Yield, wt. %                                                                  2,2-dimethylbutane 5.6    9.0                                                 ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst B                       Temperature, °C.                                                                      200    210       220  230                                      Pressure, psig 450    450       450  450                                      LHSV           0.6    0.6       0.6  0.6                                      H.sub.2 /HC    1.4/1  1.4/1     1.4/1                                                                              1.4/1                                    Hexane conv., wt. %                                                                          80.5   82.0      82.9 84.0                                     Selectivity, wt. %                                                            C.sub.1 -C.sub.5                                                                             0.4    1.2       2.0  2.8                                      2,2-dimethylbutane                                                                           12.6   14.8      19.9 21.8                                     2,3-dimethylbutane                                                                           13.0   12.6      11.8 11.6                                     2-methylpentane                                                                              45.8   43.6      40.4 37.8                                     3-methylpentane                                                                              28.2   27.8      25.9 23.9                                     Yield, wt. %                                                                  2,2-dimethylbutane                                                                           10.1   12.1      16.5 18.4                                     ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst C                       Temperature, °C.                                                                          230    240                                                 Pressure, psig     450    450                                                 LHSV               0.6    0.6                                                 H.sub.2 /HC        1.4/1  1.4/1                                               Hexane conv., wt. %                                                                              80.4   81.7                                                Selectivity, wt. %                                                            C.sub.1 -C.sub.5   0.5    1.4                                                 2,2-dimethylbutane 14.7   19.0                                                2,3-dimethylbutane 12.2   11.8                                                2-methylpentane    44.1   40.9                                                3-methylpentane    28.5   26.9                                                Yield, wt. %                                                                  2,2-dimethylbutane 11.9   15.5                                                ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst D                       Temperature, °C.                                                                      200    210       220  230                                      Pressure, psig 450    450       450  450                                      LHSV           0.6    0.6       0.6  0.6                                      H.sub.2 /HC    1.4/1  1.4/1     1.4/1                                                                              1.4/1                                    Hexane conv., wt. %                                                                          81.9   82.1      83.4 84.3                                     Selectivity, wt. %                                                            C.sub.1 -C.sub.5                                                                             0.9    1.1       2.5  6.5                                      2,2-dimethylbutane                                                                           18.3   18.1      22.5 23.4                                     2,3-dimethylbutane                                                                           12.3   12.3      11.4 10.6                                     2-methylpentane                                                                              41.7   41.6      38.6 36.2                                     3-methylpentane                                                                              26.7   26.9      25.0 23.3                                     Yield, wt. %                                                                  2,2-dimethylbutane                                                                           15.0   14.8      18.8 19.7                                     ______________________________________                                    

EXAMPLE 26

This Example describes the preparation of a hydrous zirconia support.One part by weight of zirconyl chloride, ZrOCl₂. 8H₂ O, was dissolved in10 parts H₂ O and concentrated NH₄ OH.sub.(aq) added until the solutionpH was ˜9. The resulting slurry, Zr(OH)₄, was filtered and washed with10 parts of distilled, deionized water. The solid was mixed with 10parts of distilled, deionized water, and the pH of the mixture set to pH˜9 with NH₄ OH.sub.(aq). This mixture was refluxed for 16 hours, cooled,filtered, and washed with 10 parts of water. The solid was air dried at130° C. for 16 hours.

EXAMPLE 27

This Example describes the preparation of a WO_(x) /ZrO₂ catalyst fromthe zirconia support described in Example 26. Approximately 3.3 parts byweight of the dried product from Example 26 was impregnated viaincipient wetness with 2.6 parts of an aqueous solution containing 1part of ammonium metatungstate. The resulting material was dried in airand then calcined at 825° C. in air for 3 hours. The resultant productwas designated Catalyst E.

EXAMPLE 28

Catalyst F was prepared analogously to Catalyst E except 1.17 parts ofammonium metatungstate was used.

EXAMPLE 29

Catalyst G was prepared analogously to Catalyst E except 1.67 parts ofammonium metatungstate was used.

EXAMPLES 30-32

After calcining, Catalysts E, F, and G were then impregnated with Pt viaincipient wetness using a solution of 2.5 parts H₂ O and 1 part 8% H₂PtCl₆. The catalysts were air dried and then calcined at 300° C. in airfor 2 hours.

EXAMPLES 33 and 34

Catalyst E from Example 30 was tested for hexane isomerization. In twoseparate runs, prior to contacting with feed hexane, the fresh catalystwas treated with H₂ (100 cc/min) at 300° C. for 4 and 18 hours.Experimental conditions and catalyst results are given in Table 10.

EXAMPLES 35 and 36

Catalyst F from Example 31 was tested for hexane isomerizationanalogously to Examples 33 and 34. Experimental conditions and catalyticresults are given in Table 11.

EXAMPLES 37 and 38

Catalyst G from Example 32 was tested for hexane isomerization. In twoseparate runs, prior to contacting with feed hexane, the fresh catalystwas treated with H₂ (100 cc/min) at 300° C. for 4 and 72 hours.Experimental conditions and catalytic results are given in Table 12.

For Catalysts E, F, and G, increased yields of isomerized product atconstant temperature were observed with the same catalysts treated withhydrogen for 18 hours instead of 4 hours. For Catalyst G, an additionalexperiment involving H₂ pretreatement for 72 hours was performed.Although hexane isomerization activity was still present after the 72hour pretreatment, the yield of 2,2-dimethylbutane was significantlylower at constant temperature than the yields obtained after 4 hours ofH₂ pretreatment.

                  TABLE 10                                                        ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst E                                  4 hours 18 hours                                                   ______________________________________                                        Temperature, °C.                                                                    200    220    200   210  220   230                               Pressure, psig                                                                             450    450    450   450  450   450                               LHSV         0.6    0.6    0.6   0.6  0.6   0.6                               H.sub.2 /HC  1.4/1  1.4/1  1.4/1 1.4/1                                                                              1.4/1 1.4/1                             Hexane conv., wt. %                                                                        75.3   82.0   80.5  82.0 82.9  84.0                              Selectivity, wt. %                                                            C.sub.1 -C.sub.5                                                                           0.2    1.6    0.4   1.2  1.8   4.8                               2,2-dimethylbutane                                                                         8.4    16.1   12.6  14.8 19.9  21.8                              2,3-dimethylbutane                                                                         13.1   12.3   13.0  12.6 11.8  11.6                              2-methylpentane                                                                            47.8   42.4   45.7  43.5 40.5  37.9                              3-methylpentane                                                                            30.5   27.6   28.1  27.7 26.0  23.9                              Yield, wt. %                                                                  2,2-dimethylbutane                                                                         6.3    13.2   10.1  12.1 16.5  18.4                              ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst F                                  4 hours 18 hours                                                   ______________________________________                                        Temperature, °C.                                                                    210    220    230   210  220   230                               Pressure, psig                                                                             450    450    450   450  450   450                               LHSV         0.6    0.6    0.6   0.6  0.6   0.6                               H.sub.2 /HC  1.4/1  1.4/1  1.4/1 1.4/1                                                                              1.4/1 1.4/1                             Hexane conv., wt. %                                                                        81.6   82.7   83.6  82.1 83.4  84.3                              Selectivity, wt. %                                                            C.sub.1 -C.sub.5                                                                           0.4    0.9    2.5   1.1  2.5   6.5                               2,2-dimethylbutane                                                                         9.5    17.4   21.6  18.1 22.5  23.4                              2,3-dimethylbutane                                                                         12.5   12.2   11.3  12.3 11.4  10.6                              2-methylpentane                                                                            47.4   42.2   39.3  41.6 38.6  36.2                              3-methylpentane                                                                            30.2   27.3   25.4  26.9 25.0  23.3                              Yield, wt. %                                                                  2,2-dimethylbutane                                                                         6.8    14.2   17.9  14.8 18.8  19.7                              ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                        Catalytic Data for Hexane Isomerization with Catalyst G                                    4 hours        72 hours                                          Temperature, °C.                                                                      200    220       200  220                                      Pressure, psig 450    450       450  450                                      LHSV           0.6    0.6       0.6  0.6                                      H.sub.2 /HC    1.4/1  1.4/1     1.4/1                                                                              1.4/1                                    Hexane conv., wt. %                                                                          79.8   84.5      48.9 76.7                                     Selectivity, wt. %                                                            C.sub.1 -C.sub.5                                                                             0.5    3.1       0.0  0.4                                      2,2-dimethylbutane                                                                           14.5   25.1      2.6  10.9                                     2,3-dimethylbutane                                                                           21.0   11.3      11.1 12.7                                     2-methylpentane                                                                              36.6   37.3      52.9 46.1                                     3-methylpentane                                                                              27.4   23.3      33.4 29.9                                     Yield, wt. %                                                                  2,2-dimethylbutane                                                                           11.6   21.3      1.3  8.44                                     ______________________________________                                    

What is claimed is:
 1. A catalyst consisting essentially of (i) ahydrogenation/dehydrogenation component comprising a noble metal and(ii) an acidic solid component comprising zirconium oxide modified withan oxyanion of a Group VIB metal.
 2. A catalyst according to claim 1,wherein said hydrogenation/dehydrogenation component, in addition tosaid noble metal, further comprises at least one non-noble metal in theform of at least one oxide, hydroxide or metal of at least one elementselected from the group consisting of Group VIII metals, Group IVAmetals, Group VB metals and Group VIIB metals.
 3. A catalyst accordingto claim 1, wherein said hydrogenation/dehydrogenation componentcomprises platinum.
 4. A catalyst according to claim 1, wherein saidhydrogenation/dehydrogenation component further comprises tin.
 5. Acatalyst according to claim 1, wherein said Group VIB metal oxyanion isan oxyanion of molybdenum or tungsten.
 6. A catalyst according to claim1, wherein said hydrogenation/dehydrogenation component comprisesplatinum in the form of an oxide, hydroxide or free metal, and saidGroup VIB metal oxyanion is tungstate.
 7. A catalyst according to claim1 comprising a calculated mole ratio of XO₂ /YO₃, where X is saidzirconium and Y is said Group VIB metal, of up to 300 and from 0.001 wt% to about 5 wt % of said hydrogenation/dehydrogenation component, basedupon the total weight of the catalyst.
 8. A catalyst according to claim6 comprising a calculated mole ratio of XO₂ /YO₃, where X is saidzirconium and Y is said Group VIB metal, of from 2 to 100 and from 0.001wt % to about 5 wt % of said hydrogenation/dehydrogenation component,based upon the total weight of the catalyst.
 9. A catalyst according toclaim 6 comprising a calculated mole ratio of XO₂ /YO₃, where X is saidzirconium and Y is said Group VIB metal, of from 4 to 30 and from 0.1 wt% to about 2 wt % of platinum, based upon the total weight of thecatalyst.
 10. A method for preparing a catalyst consisting essentiallyof (i) a hydrogenation/dehydrogenation component comprising a noblemetal and (ii) an acidic solid component comprising zirconium oxidemodified with an oxyanion of a Group VIB metal, said method consistingessentially of the steps of:(a) contacting a hydroxide or hydrated oxideof zirconium with an aqueous solution comprising an oxyanion of a GroupVIB metal under conditions sufficient to form a solid materialcomprising oxygen, zirconium and Group VIB metal; and (b) combining saidsolid material of step (a) with a noble metal.
 11. A method according toclaim 10, wherein said aqueous solution of step (a) comprises a sourceof said oxyanion of a Group VIB metal which is (NH₄)₂ WO₂ or WCl₆.
 12. Amethod according to claim 10, wherein said aqueous solution of step (a)comprises a source of said oxyanion of a Group VIB metal which isselected from the group consisting of ammonium metatungstate, ammoniummetamolybdate, tungsten chloride, molybdenum chloride, tungstencarbonyl, molybdenum carbonyl, tungstic acid, sodium tungstate andsodium molybdate.
 13. A method according to claim 10, wherein thehydroxide of said zirconium is contacted with said aqueous solutionaccording to step (a).
 14. A method according to claim 13, wherein,prior to step (b), said solid material of step (a) is calcined underconditions sufficient to convert said hydroxide of said zirconium to anoxide of said zirconium.
 15. A method according to claim 14, whereinstep (b) comprises impregnating the calcined solid material of step (a)with H₂ PtCl₆.
 16. A method according to claim 13, wherein step (b)comprises impregnating the uncalcined solid material of step (a) with H₂PtCl₆.
 17. A method according to claim 16, wherein the H₂ PtCl₆impregnated material of step (b) is calcined under conditions sufficientto convert said hydroxide of said zirconium to an oxide of saidzirconium and to convert H₂ PtCl₆ to platinum oxide, followed bysubjecting the catalyst to reducing conditions sufficient to convertplatinum to the metallic state.